methylcellulose and Dental-Caries

Incipient caries lesions on smooth surfaces may be subjected to toothbrushing, potentially leading to remineralization and/or abrasive wear. The interplay of dentifrice abrasivity and fluoride on this process is largely unknown and was investigated on three artificially created lesions with different mineral content/distribution. 120 bovine enamel specimens were randomly allocated to 12 groups (n = 10), resulting from the association of (1) lesion type [methylcellulose acid gel (MeC); carboxymethylcellulose solution (CMC); hydroxyethylcellulose gel (HEC)], (2) slurry abrasive level [low (REA 4/ RDA 69); high (REA 7/RDA 208)], and (3) fluoride concentration [0/275 ppm (14.5 mM) F as NaF]. After lesion creation, specimens were brushed in an automated brushing machine with the test slurries (50 strokes 2×/day). Specimens were kept in artificial saliva in between brushings and overnight. Enamel surface loss (SL) was determined by optical profilometry after lesion creation, 1, 3 and 5 days. Two enamel sections (from baseline and post-brushing areas) were obtained and analyzed microradiographically. Data were analyzed by analysis of variance and Tukey's tests (α = 5%). Brushing with high-abrasive slurry caused more SL than brushing with low-abrasive slurry. For MeC and CMC lesions, fluoride had a protective effect on SL from day 3 on. Furthermore, for MeC and CMC, there was a significant mineral gain in the remaining lesions except when brushed with high-abrasive slurries and 0 ppm F. For HEC, a significant mineral gain took place when low-abrasive slurry was used with fluoride. The tested lesions responded differently to the toothbrushing procedures. Both slurry fluoride content and abrasivity directly impacted SL and mineral gain of enamel caries lesions.

Topics: Animals; Carboxymethylcellulose Sodium; Cariostatic Agents; Cattle; Cellulose; Dental Caries; Dental Enamel; Dentifrices; Gels; Methylcellulose; Microradiography; Minerals; Protective Agents; Random Allocation; Saliva, Artificial; Sodium Fluoride; Tooth Abrasion; Tooth Remineralization; Toothbrushing

Acid gel caries lesions were created in 3,100 human and bovine enamel specimens and studied with transverse microradiography. Small, significant differences were found. Human enamel lesions were found to be less demineralized, shallower, had a higher ratio of integrated mineral loss (ΔZ) to lesion depth (L), a lower degree of surface zone mineralization (SZ(max)) and showed less variability than those in bovine enamel. SZ(max) showed the highest variability. Between tissues, L differed the most, ΔZ the least. Biological variation within bovine enamel is perhaps not only bigger than previously assumed, it may also overshadow any structural and chemical differences between tissues.

Topics: Animals; Cattle; Dental Caries; Dental Enamel; Dentin; Humans; Hydrogen-Ion Concentration; Lactic Acid; Methylcellulose; Microradiography; Minerals; Tooth Demineralization

The present mechanistic in vitro study aimed to investigate dose-response effects of zinc and fluoride on caries lesion remineralization and subsequent protection from demineralization. Artificial caries lesions were created using a methylcellulose acid gel system. Lesions were remineralized for 2 weeks using citrate-containing artificial saliva which was supplemented with zinc (0-153 μmol/l) and fluoride (1.1 or 52.6 μmol/l) in a 7 × 2 factorial design. Lesions were also remineralized in the absence of zinc and citrate, but in the presence of fluoride. After remineralization, all lesions were demineralized for 1 day under identical conditions. Changes in mineral distribution characteristics of caries lesions after remineralization and secondary demineralization were studied using transverse microradiography. At 1.1 μmol/l fluoride, zinc exhibited detrimental effects on remineralization in a dose-response manner and mainly by preventing remineralization near the lesion surface. At 52.6 μmol/l fluoride, zinc retarded remineralization only at the highest concentration tested. Zinc enhanced overall remineralization at 3.8-15.3 μmol/l. At 76.5 and less so at 153 μmol/l, zinc showed extensive remineralization of deeper parts within the lesions at the expense of remineralization near the surface. Citrate did not interfere with remineralization at 1.1 μmol/l fluoride, but enhanced remineralization at 52.6 μmol/l fluoride. Lesions exhibiting preferential remineralization in deeper parts showed higher mineral loss after secondary demineralization, suggesting the formation of more soluble mineral phases during remineralization. In summary, zinc and fluoride showed synergistic effects in enhancing lesion remineralization, however only at elevated fluoride concentrations.

Topics: Animals; Apatites; Calcium Fluoride; Calcium Phosphates; Cariostatic Agents; Cattle; Citric Acid; Dental Caries; Dental Enamel; Dental Enamel Solubility; Dose-Response Relationship, Drug; Drug Synergism; Durapatite; Fluorides; Hydrogen-Ion Concentration; Lactic Acid; Methylcellulose; Microradiography; Minerals; Phosphates; Saliva, Artificial; Tooth Remineralization; Zinc; Zinc Compounds

This study investigated the effects of lesion baseline characteristics and different strontium (Sr) to calcium (Ca) ratios in plaque fluid-like solutions (PF) on lesion de- and remineralization. Caries lesions were formed in enamel using three protocols: methylcellulose acid gel (MeC) and partially saturated lactic acid solutions containing carboxymethylcellulose (CMC) or not (SOLN). Lesions were exposed to PF with four distinct Sr:Ca molar ratios (0:1/3:1:3), but otherwise identical composition and total Sr+Ca molarity, for seven days. Lesions were characterized using transverse microradiography (TMR) at baseline and post-treatment. At baseline, MeC and CMC had similar integrated mineral loss values, whereas SOLN lesions were more demineralized. All lesions showed significant differences in their mineral distributions, with CMC and SOLN having lower R values (integrated mineral loss to lesion depth ratio) than MeC. Post-PF exposure, no interaction was found between lesion type and Sr:Ca ratio. Within lesion type, MeC demineralized, whereas CMC and SOLN exhibited some remineralization, with the differences between MeC and the other lesion types being of statistical significance. Within Sr:Ca ratio, the 1:3 ratio exhibited some remineralization whereas other groups tended to demineralize. Only the difference between groups SrCa1/3 and SrCa0 was of statistical significance. In summary, both lesion baseline characteristics and Sr:Ca ratio were shown to effect lesion de- and remineralization. Under the conditions of the study, high-R lesions are more prone to demineralize under PF-like conditions than low-R lesions. In addition, partial Sr substitution for Ca in PF was shown to enhance lesion remineralization.

Topics: Analysis of Variance; Animals; Calcium Chloride; Cattle; Dental Caries; Dental Plaque; In Vitro Techniques; Lactic Acid; Methylcellulose; Microradiography; Solutions; Strontium; Tooth Demineralization; Tooth Remineralization

The aim was to study the effects of zinc (Zn) and fluoride (F) on remineralisation at plaque fluid concentrations. Artificial carious lesions were created in 2 acid-gel demineralising systems (initially infinitely undersaturated and partially saturated with respect to enamel) giving lesions with different mineral distribution characteristics (high and low R values, respectively) but similar integrated mineral loss values. Lesions of both types were assigned to 1 of 4 groups and remineralised for 5 days at 37°C. Zn and F were added, based on plaque fluid concentrations 1 h after application, to give 4 treatments: 231 μmol/l Zn, 10.5 μmol/l F, Zn/F combined and an unmodified control solution (non-F/non-Zn). Subsequently remineralisation was measured using microradiography. High-R lesions were analysed for calcium, phosphorus, F and Zn using electron probe micro-analysis. All lesions underwent statistically significant remineralisation. For low-R lesions, remineralisation was in the order F(a) < non-F/non-Zn(a) < Zn(a, b) < Zn/F(b), and for high-R lesions F(a) < non-F/non-Zn(b) < Zn(b) < Zn/F(c) (treatments with the same superscript letter not significantly different, at p < 0.05). Qualitatively, remineralisation occurred throughout non-F/non-Zn and Zn groups, predominantly at the surface zone (F) and within the lesion body (Zn/F). Electron probe micro-analysis revealed Zn in relatively large amounts in the outer regions (Zn, Zn/F). F was abundant not only at the surface (F), but also in the lesion body (Zn/F). Calcium:phosphate ratios were similar to hydroxyapatite (all). To conclude, under static remineralising conditions simulating plaque fluid, Zn/F treatment gave significantly greater remineralisation than did F treatment, possibly because Zn in the Zn/F group maintained greater surface zone porosity compared with F, facilitating greater lesion body remineralisation.

Topics: Animals; Calcium; Cariostatic Agents; Cattle; Dental Caries; Dental Enamel; Dental Plaque; Durapatite; Electron Probe Microanalysis; Fluorides; Hydrogen-Ion Concentration; Lactic Acid; Methylcellulose; Microradiography; Phosphorus; Spectrometry, X-Ray Emission; Temperature; Time Factors; Tooth Remineralization; Zinc

The aims of this study were: (1) to correlate surface (SH) and cross-sectional hardness (CSH) with microradiographic parameters of artificial enamel lesions; (2) to compare lesions prepared by different protocols. Fifty bovine enamel specimens were allocated by stratified randomisation according to their initial SH values to five groups and lesions produced by different methods: MC gel (methylcellulose gel/lactic acid, pH 4.6, 14 days); PA gel (polyacrylic acid/lactic acid/hydroxyapatite, pH 4.8, 16 h); MHDP (undersaturated lactate buffer/methyl diphosphonate, pH 5.0, 6 days); buffer (undersaturated acetate buffer/fluoride, pH 5.0, 16 h), and pH cycling (7 days). SH of the lesions (SH(1)) was measured. The specimens were longitudinally sectioned and transverse microradiography (TMR) and CSH measured at 10- to 220-microm depth from the surface. Overall, there was a medium correlation but non-linear and variable relationship between mineral content and radicalCSH. radicalSH(1) was weakly to moderately correlated with surface layer properties, weakly correlated with lesion depth but uncorrelated with integrated mineral loss. MHDP lesions showed the highest subsurface mineral loss, followed by pH cycling, buffer, PA gel and MC gel lesions. The conclusions were: (1) CSH, as an alternative to TMR, does not estimate mineral content very accurately, but gives information about mechanical properties of lesions; (2) SH should not be used to analyse lesions; (3) artificial caries lesions produced by the protocols differ, especially considering the method of analysis.

Topics: Acetates; Acrylic Resins; Anatomy, Cross-Sectional; Animals; Apatites; Buffers; Calcium Phosphates; Cariogenic Agents; Cariostatic Agents; Cattle; Dental Caries; Dental Enamel; Diphosphonates; Durapatite; Fluorides; Gels; Hardness; Hydrogen-Ion Concentration; Lactic Acid; Methylcellulose; Microradiography; Random Allocation; Solutions; Time Factors; Tooth Demineralization; Tooth Remineralization

A modified acid gel technique for producing caries-like lesions in dental enamel has been developed. The decalcifying medium consists of a 10% (w/v) methylcellulose gel acidified with 0.1 M lactic acid-sodium lactate at pH 4.5 and having a hydroxyapatite content of 0.05% (w/v). This medium can produce caries-like lesions in vitro at a slow rate, which are indistinguishable from natural enamel caries when examined by polarised light microscopy and contact microradiography.

Topics: Adolescent; Bicuspid; Cariogenic Agents; Dental Caries; Dental Enamel; Durapatite; Gels; Humans; Hydroxyapatites; In Vitro Techniques; Methylcellulose

The rehardening properties of four saliva substitutes on artificially softened human enamel have been investigated by microhardness measurements. The saliva substitutes were all based on the same formula, containing calcium, phosphate and fluoride as the main electrolytes, and mucin or carboxymethylcellulose as the main macromolecules. It has been shown that a rehardening potential exists in the saliva substitutes when calcium and phosphate are present. Omitting F- greatly reduces the rehardening potential. The rehardening is better in case of the CMC-containing saliva than in that containing mucin.

Topics: Carboxymethylcellulose Sodium; Dental Caries; Dental Enamel; Hardness; Humans; Methylcellulose; Mouthwashes; Mucins; Saliva, Artificial; Time Factors; Tooth Calcification

Topics: Carboxymethylcellulose Sodium; Dental Caries; Dental Enamel; Humans; Methylcellulose; Models, Biological

Topics: Calcium Hydroxide; Dental Caries; Dental Cavity Lining; Dental Pulp; Dentin, Secondary; Methylcellulose; Radiography

Topics: Calcium Hydroxide; Child; Dental Caries; Dental Pulp Capping; Dentin; Hardness Tests; Humans; Methylcellulose; Molar; Tooth Calcification; Tooth, Deciduous; Zinc Oxide-Eugenol Cement